In order to increase the backward momentum and thus make possible an increase in the weight of the ammunition part without excessively high pressure being created behind the weapon, it has been known for many years to introduce what is known as a countermass. When the countermass leaves the rear part of the barrel, it expands and disintegrates. A liquid cloud is formed, which is braked rapidly and produces a pressure-reducing effect adjacent to the weapon. In this connection, reference may be made to our SE patent 8205956-9 which shows an example of a weapon with countermass. Constructions with countermass are found in weapons of both single-use and multiple-use type.
During the operation when the countermass is pushed out of the barrel and any expansion part by gas pressure, it is important that the material in the countermass helps to hold the countermass together so that the transport out through the outlet of the barrel is as much in the form of a solid lump as possible without being so. In connection with the countermass being enclosed in the container, it is virtually inevitable that a certain amount of air is also enclosed. In general, it is important that as little air as possible is enclosed. Even if no large quantities of air are enclosed in known containers of countermass, the enclosed air can nevertheless cause problems. A known phenomenon is for the air to collect in the upper part of the container, which renders the countermass asymmetrical and leads to interference with the weapon when the shell is fired, which has a negative effect on the probability of the shell hitting the target. Another known phenomenon is for continuous air passages to be formed in the countermass. These air passages allow gas flowthrough and result in impaired functioning of the countermass.